The invention pertains to suspensions for railway and non-railway vehicles, for cushioning shocks on an axle assembly caused by irregularities in the track or ground, before they can be transmitted to the frame.
Personnel, and some supplies, are transported about underground mines in battery-or trolley-powered personnel cars, sometimes called portal buses, having flanged railway-type wheels running on mine track. Most mine track undulates because it is not economical to install it with above-ground precision, or to lay on a deep, stable foundation. And, once installed, the track condition worsens in use because of irregular heaving or swelling of the mine bottom, roof falls, and the constant back and forth movements of mine cars and locomotives. It is not unusual in a modern large mine for men to be transported in personnel cars as much as three to five miles to their working places. This can require a ride of up to an hour at the beginning of the shift and again at the end of the shift, during which time the miners are confined to the car, often in prone or crouched positions to clear the roof and supporting beams.
Up to a few years ago, men were transported to and from the working place in empty mine cars. Sometimes they walked, or even crawled part way. Use of mine cars and locomotives for this purpose diverted production machinery from its primary purpose; further, cars made for hauling and dumping coal and ore were not comfortable and sometimes not even safe. Occasionally, to go between working areas during a shift, a few men would hitch a ride on the top of a spare locomotive or in a mine car which, designed for one operator and one or two helpers, was not safe for several more. It has been only recently that special personnel cars have been made just for transporting men, andthey are manufactured strictly for that purpose with comfort features such as cushioning and roominess secondary. In some personnel cars, one or more axles are trunnion-mounted, rocking about longitudinal pivotal connections to the frame in the center of the car. This eliminates the requirement for journal boxes and allows the vehicle to adapt to varying track conditions and to negotiate curves without derailment. It saves cost and in some cases lowers the headroom required for the car. However, although the trunnion mount enables the axle assembly to rock about pivotal connections to accommodate up and down irregularities in the track or ground, the pivotal connections fore and aft of the axle housing are solidly connected to the frame and transmit shocks, uncushioned, directly from the axle assembly to the frame and to the men riding inside. This can be most uncomfortable on a long trip underground, especially when it is repeated day after day.